src: throw when -c and -e are used simultaneously

The -c flag ("check script syntax") and -e flag ("evaluate given code")
have contradictory meanings. Make them mutually exclusive by throwing
when both of them are provided.

Fixes: nodejs#11680
PR-URL: nodejs#11689
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

src/node.cc

@@ -3816,6 +3816,12 @@ static void ParseArgs(int* argc,
   }
 #endif
 
+  if (eval_string != nullptr && syntax_check_only) {
+    fprintf(stderr,
+            "%s: either --check or --eval can be used, not both\n", argv[0]);
+    exit(9);
+  }
+
   // Copy remaining arguments.
   const unsigned int args_left = nargs - index;
   memcpy(new_argv + new_argc, argv + index, args_left * sizeof(*argv));

test/parallel/test-cli-syntax.js

@@ -99,7 +99,7 @@ syntaxArgs.forEach(function(args) {
   assert.strictEqual(c.status, 0, 'code === ' + c.status);
 });
 
-// should should throw if code piped from stdin with --check has bad syntax
+// should throw if code piped from stdin with --check has bad syntax
 // loop each possible option, `-c` or `--check`
 syntaxArgs.forEach(function(args) {
   const stdin = 'var foo bar;';
@@ -117,3 +117,18 @@ syntaxArgs.forEach(function(args) {
 
   assert.strictEqual(c.status, 1, 'code === ' + c.status);
 });
+
+// should throw if -c and -e flags are both passed
+['-c', '--check'].forEach(function(checkFlag) {
+  ['-e', '--eval'].forEach(function(evalFlag) {
+    const args = [checkFlag, evalFlag, 'foo'];
+    const c = spawnSync(node, args, {encoding: 'utf8'});
+
+    assert.strictEqual(
+      c.stderr,
+      `${node}: either --check or --eval can be used, not both\n`
+    );
+
+    assert.strictEqual(c.status, 9, 'code === ' + c.status);
+  });
+});